Re: [PATCH v4 1/4] dt-bindings: interconnect: qcom,sdm845-cpu-bwmon: add BWMON device

[Rajendra Nayak]

On 6/7/2022 12:20 PM, Krzysztof Kozlowski wrote:
> On 06/06/2022 23:11, Bjorn Andersson wrote:
> > On Wed 01 Jun 03:11 PDT 2022, Krzysztof Kozlowski wrote:
> >
> > > Add bindings for the Qualcomm Bandwidth Monitor device providing
> > > performance data on interconnects.  The bindings describe only BWMON
> > > version 4, e.g. the instance on SDM845 between CPU and Last Level Cache
> > > Controller.
> > >
> > > Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> > > Reviewed-by: Rob Herring <robh@xxxxxxxxxx>
> > > Acked-by: Georgi Djakov <djakov@xxxxxxxxxx>
> > > ---
> > >   .../interconnect/qcom,sdm845-cpu-bwmon.yaml   | 97 +++++++++++++++++++
> > >   1 file changed, 97 insertions(+)
> > >   create mode 100644 Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml
> > >
> > > diff --git a/Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml b/Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml
> > > new file mode 100644
> > > index 000000000000..8c82e06ee432
> > > --- /dev/null
> > > +++ b/Documentation/devicetree/bindings/interconnect/qcom,sdm845-cpu-bwmon.yaml
> > > @@ -0,0 +1,97 @@
> > > +# SPDX-License-Identifier: GPL-2.0-only OR BSD-2-Clause
> > > +%YAML 1.2
> > > +---
> > > +$id: http://devicetree.org/schemas/interconnect/qcom,sdm845-cpu-bwmon.yaml#
> > > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > > +
> > > +title: Qualcomm Interconnect Bandwidth Monitor
> > > +
> > > +maintainers:
> > > +  - Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
> > > +
> > > +description:
> > > +  Bandwidth Monitor measures current throughput on buses between various NoC
> > > +  fabrics and provides information when it crosses configured thresholds.
> > > +
> > > +properties:
> > > +  compatible:
> > > +    enum:
> > > +      - qcom,sdm845-cpu-bwmon       # BWMON v4
> >
> > It seems the thing that's called bwmon v4 is compatible with a number of
> > different platforms, should we add a generic compatible to the binding
> > as well, to avoid having to update the implementation for each SoC?
> >
> > (I.e. "qcom,sdm845-cpu-bwmon", "qcom,bwmon-v4")

it seems pretty useful to have the "qcom,bwmon-v4" and "qcom,bwmon-v5"
compatibles, I tried these patches on a sc7280 device which has a bwmon4
between the cpu and caches (and also has a bwmon5 between the caches and DDR)
and the driver works with zero changes.

> I am hesitant. I could not find BWMON IP block versioning in the
> Qualcomm docs. Only the downstream sources had it. Therefore I think it
> is more applicable to use this one as fallback for other boards, e.g.:
>
> "qcom,sdm660-cpu-bwmon", "qcom,sdm845-cpu-bwmon"
> (even if the number is a bit odd - newer comes as last compatible).
>
> What's your preference?
>
> Best regards,
> Krzysztof